Optically Stimulated Luminescence (OSL) Dating of Alluvial Deposits from the Cahuachi Archaeological Site (South Peru)

Cahuachi (Nazca River Valley, South Peru) was the major ceremonial center of the Nasca civilization. According to previous studies, it was struck and destroyed by three El Niño-Southern Oscillation events, which would have occurred around 100 BCE, 600 CE and 1000 CE, respectively. At the end of the series of events, the ceremonial center would have been buried by a cap of conglomerates. Despite this hypothesis raised well-founded doubts regarding its geochronological and paleoenvironmental implications, it is uncritically used as a reference in geoarchaeological research. In the present study, optically stimulated luminescence (OSL) dating results of some samples taken from alluvial deposits at Cahuachi are reported, with the aim to evaluate the literature’s hypothesis. Since the obtained ages are older than the Holocene epoch, such a hypothesis must be rejected. A number of field evidences corroborate this result. Finally, the advancement in fluvial geomorphology knowledge of the Nazca River Valley is briefly discussed.